I. Field of the Invention
The present invention relates generally to metal working tools, and more particularly to metal punch assemblies used in high speed, turret-type punch presses.
II. Discussion of the Prior Art
As is well known in the art, turret-type punch presses typically comprise an upper rotatable disk carrying a plurality of punch assemblies of varying sizes and shapes and a lower rotatable disk carrying a plurality of dies, each including a through-bore also of varying sizes and shapes. The workpiece commonly is a piece of sheet metal that is disposed between the punch assemblies and the dies. The turrets are made to rotate under computer control until a programmably selected punch assembly is aligned across the workpiece with a programmably selected die at a desired orbital location, whereupon the punch is driven through the workpiece into the die.
A punch assembly commonly comprises an outer punch guide member having a longitudinal bore formed through it and disposed in the bore, and confined to reciprocating, but often non-rotating movement is a punch member comprising a shank with a punch point affixed to it. Also, it is known to provide a heavy return spring operatively disposed between the shank and the punch guide member that returns the punch member to its raised position following a punching stroke.
As a matter of economics, it is also a known practice to have a two-piece punch, having a low-cost steel shank to which is releasably attached a more expensive, hardened, tool-steel punch point member. It is the punch point member that engages the workpiece and drives a slug through a die during operation of the machine.
After repeated strokes, the punch point member may become dull and require sharpening or replacement. In order not to slow down production, a need exists for a way to quickly remove and replace a punch point member from and onto its shank.
Although the prior art discloses various ways of coupling a punch point member to its shank in forming a punch assembly, a need persists for a design that helps assure efficient removal and replacement of a punch point member from its shank.